Adaptive Polarimetric Radar Architecture for Autonomous Driving

ABSTRACT

An antenna includes a plurality of waveguide antenna elements arranged in a first array configured to operate with a first polarization. The antenna also includes a plurality of waveguide output ports arranged in a second array configured to operate with a second polarization. The second polarization is different from the first polarization. The antenna further includes a polarization-modification layer with channels defined therein. The polarization-modification layer is disposed between the waveguide antenna elements and the waveguide output ports. The channels are oriented at a first angle with respect to the waveguide antenna elements and at a second angle with respect to the waveguide output ports. The channels are configured to receive input electromagnetic waves having the first polarization and transmit output electromagnetic waves having a first intermediate polarization. The waveguide output ports are configured to receive input electromagnetic waves and radiate electromagnetic waves having the second polarization.

CROSS REFERENCE TO RELATED APPLICATION

The present patent application is a continuation of U.S. patentapplication Ser. No. 15/842,704, filed on Dec. 14, 2017, which is herebyincorporated by reference in entirety.

BACKGROUND

Radio detection and ranging (RADAR) systems can actively estimatedistances to features in the environment by emitting radio signals anddetecting returning reflected signals that reflect off surfaces in theenvironment. As a result, distances to radio-reflective features can bedetermined according to the time delay between transmission andreception. The radar system can emit a signal that varies in frequencyover time, such as a signal with a time-varying frequency ramp, and thenrelate the difference in frequency between the emitted signal and thereflected signal to a range estimate.

Some systems may also estimate relative motion of reflective objectsbased on Doppler frequency shifts in the received reflected signals.Directional antennas (e.g., array antennas) can be used for thetransmission and/or reception of signals to associate each rangeestimate with a bearing. More generally, directional antennas can alsobe used to focus radiated energy on a given field of view of interest.Combining the measured distances and the directional information allowsfor the surrounding environment features to be identified and/or mapped.The radar sensor can thus be used, for instance, by an autonomousvehicle control system to avoid obstacles indicated by the sensorinformation.

SUMMARY

Examples embodiments involve adjusting the polarization of one ormultiple antennas operating on a radar unit. In some examples, adjustingthe polarization of a radar antenna involves using a polarization filterthat causes the antenna to transmit or receive radar signals radiatingin a polarization that differs from the polarization that the antennawas originally designed for. For instance, a polarization filter can beattached to or generated within a radar unit to cause one or multipleantennas to operate within a different polarization. In other examples,adjusting the polarization of a radar antenna involves modifying theinner configuration of the radar unit during development of the radarunit in order to twist (e.g., modify) the polarization of the radarantenna. For instance, the additional twist modification within a radarunit can cause electromagnetic waves traversing inside the radar unit totwist in order to output at a desired polarization.

In one aspect, the present application describes a radar unit. The radarunit includes a plurality of transmission antennas configured totransmit radar signals having a first polarization, and a plurality ofreception antennas configured to receive radar signals having the firstpolarization. The radar unit also includes a polarization filter coupledto at least a portion of the plurality of transmission antennas and theplurality of reception antenna. Particularly, the polarization filtercauses a subset of the transmission antennas of the plurality oftransmission antennas to transmit radar signals having a secondpolarization, and wherein the polarization filter causes a subset of thereception antennas of the plurality of reception antennas to receiveradar signals having the second polarization.

In another aspect, the present application describes a radar system. Theradar system includes a plurality of transmission antenna configured totransmit radar signals having a first polarization and a plurality ofreception antennas configured to receive radar signals having the firstpolarization. The radar system also includes a polarization filtercoupled to at least a portion of the plurality of transmission antennasand the plurality of reception antennas. Particularly, the polarizationfilter causes a subset of the transmission antennas of the plurality oftransmission antennas to transmit radar signals having a secondpolarization. In addition, the polarization filter also causes a subsetof the reception antennas of the plurality of reception antennas toreceive radar signals having the second polarization.

In yet another aspect, the present application describes a method ofsignaling with a radar system. The method includes transmitting one ormore radar signals using an array of transmission antennas. Forinstance, the array of transmission antennas is configured to transmitradar signals having a first polarization. Additionally, a polarizationfilter is coupled to the array of transmission antennas and causes thearray of transmission antennas to transmit the one or more radar signalshaving a second polarization. The method further includes receiving theone or more radar signals using an array of reception antennas. Forinstance, the array of reception antennas is configured to receive radarsignals having the first polarization. Further, the polarization filteris coupled to the array of reception antennas and causes the array ofreception antennas to receive the one or more radar signals having thesecond polarization.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the figures and the followingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a unit cell of a polarization filter, according toexample embodiments.

FIG. 2 illustrates a unit cell of a polarization filter and a waveguide,according to example embodiments.

FIG. 3 illustrates a unit cell of a polarization filter and twowaveguides, according to example embodiments.

FIG. 4 illustrates a waveguide, a unit cell of a polarization filter,and a horn antenna, according to example embodiments.

FIG. 5 illustrates a unit cell of another polarization filter, accordingto example embodiments.

FIG. 6 illustrates a unit cell of another polarization filter and twowaveguides, according to example embodiments.

FIG. 7 illustrates a polarization filter layer, according to exampleembodiments.

FIG. 8A illustrates a wave-radiating portion of an antenna, according toexample embodiments.

FIG. 8B illustrates another antenna, according to example embodiments.

FIG. 9 illustrates an array of open ended waveguide antenna elements,according to example embodiments.

FIG. 10 illustrates another array of open ended waveguide antennaelements and a polarization filter, according to example embodiments.

FIG. 11 illustrates an array of waveguide antenna elements, apolarization filter, and an array of waveguide output ports, accordingto example embodiments.

FIG. 12A illustrates a twisted antenna configuration, according toexample embodiments.

FIG. 12B illustrates another twisted antenna configuration, according toexample embodiments.

FIG. 13 illustrates a twisted antenna, according to example embodiments.

FIG. 14 illustrates a method of radiating electromagnetic waves,according to example embodiments.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying figures, which form a part hereof. In the figures, similarsymbols typically identify similar components, unless context dictatesotherwise. The illustrative embodiments described in the detaileddescription, figures, and claims are not meant to be limiting. Otherembodiments may be utilized, and other changes may be made, withoutdeparting from the scope of the subject matter presented herein. It willbe readily understood that the aspects of the present disclosure, asgenerally described herein, and illustrated in the figures, can bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are explicitlycontemplated herein.

As discussed above, a radar system can use one or multiple transmissionantennas to emit radar signals in predetermined directions to measurethe environment. Upon coming into contact with surfaces in theenvironment, the radar signals can reflect or scatter in multipledirections. A portion of the radar signals may reflect back towards theradar system and are captured by one or multiple reception antennas.Received reflected signals can then be processed to determine locationsof surfaces relative to the radar system.

Due to the ability to measure distances to features as well as motion ofmoving features within an environment (e.g., motion of the movingfeature, relative motion of the feature with respect to the radarplatform, and/or a combination of motion), radar systems areincreasingly used to assist with vehicle navigation and safety.Particularly, vehicles may rely upon a radar system during autonomous orsemi-autonomous operation to enable a vehicle control system to detect,for example, nearby vehicles, road boundaries, weather conditions,traffic signs and signals, and pedestrians, among other features withinthe environment surrounding the vehicle. As the number of vehicle radarsystems continues to grow, there is a desire for affordable radar unitsthat can accurately measure the surrounding environment of the radar,e.g., the surrounding environment of a vehicle, and also operate in anenvironment with multiple vehicles having radar systems.

Example embodiments presented herein include low-cost radar units thatcan mount at various positions and orientations on a vehicle to captureaccurate measurements of the vehicle's environment. Particularly, someexample radar units described herein may include one or multiplepolarization filters that can manipulate the polarizations in which thetransmission and reception antennas transmit or receive radar signals.As such, the position, configuration, and influence that a polarizationfilter has on a radar unit can vary within examples.

To illustrate an example implementation, a radar unit may include atransmission array and a reception array with each array consisting ofone or multiple antennas configured to initially transmit or receiveradar signals in particular polarizations. Polarization, such as thepolarization of a radar signal, represents a property that applies totransverse waves (e.g., electromagnetic radar signals). In particular,polarization specifies the geometrical orientation of the oscillationsof a transverse wave. For instance, linear polarization is theconfinement of the electric field vector to a given plane along thedirection of propagation.

To further elaborate, if a radar signal has a vertical orientationduring travel (i.e., the radar signal alternates in an up and down pathas the signal travels), the radar signal can be described as a verticallinear polarized radar signal. When a radar signal has a horizontalorientation during travel (i.e., the radar signal alternates betweenside to side along a parallel plane as the signal travels), the radarsignal can be described as a horizontal linear polarized radar signal.These polarizations are not the only possible polarizations that radarsignals may traverse. Rather, radar signals can also travel along otherpolarizations, such as slanted polarizations that traverse betweenhorizontal linear and vertical linear polarizations. For example, aradar signal traveling at a slanted polarization may travel at positiveor negative forty-five (45) degrees from a horizontal plane.

As such, radar units are often designed such that antennas transmit andreceive in particular polarizations. For instance, a radar unit mayinclude an array of transmission antennas and an array of receptionantennas that both transmit or receive radar signals in a particularpolarization (e.g., vertical linear polarization). Radar units cansometimes have a particular design to enable mass production. In thesesituations, although a radar unit can capture measurements in aparticular polarization, the radar unit might be unable to capturemeasurements in other polarizations. As a result, a radar systemoperating on a vehicle or other entity may benefit from additional radarunits designed to transmit and receive in other polarizations in orderto enable the radar system to measure the environment in multiplepolarizations.

Some examples presented herein include using polarization filters thatenable radar units designed to operate in a particular polarization orpolarizations to operate in other polarizations. Thus, although thetransmission array and/or reception array of a radar unit may includeantennas configured to transmit or receive radar signals in a particularpolarization or polarizations, the radar unit may further include one ormultiple polarization filters that can alter the polarization that allor some of the antennas transmit and/or receive radar signals.

A polarization filter can couple to various positions relative toradiating antennas in order to manipulate the polarity of the antennas.For instance, the polarization filter can couple to the radar unitdirectly under radiating elements or in another layer of the radar unit.Additionally, a polarization filter can also adjust the polarization ofa transmitting or receiving antenna to various degrees. For instance, aradar unit can be configured with one or multiple polarization filtersto adjust from transmitting (and receiving) multiple signals in a givenpolarization to another polarization that is orthogonal to originalpolarization of the radar unit design.

When a signal is orthogonal to another signal, this means that eachsignal is capable of being resolved independently of the other signaldue to the way each signal traverses through the environment. Forexample, when a radar unit transmits both vertically linear polarizedand horizontally linear polarized signals, these signals may beorthogonal to each other. In practice, the two orthogonal can bereflected by objects in the environment and received by the radar unit.As such, the vertically polarized reflection signals may be received bya vertically polarized antenna and the horizontally polarized reflectionsignals may be received by a horizontally polarized antenna. Because avertically polarized signal is orthogonal to a horizontally polarizedsignal, a vertically polarized antenna will receive none (or a verysmall percentage) of a horizontally polarized signal and a horizontallypolarized antenna will receive none (or a very small percentage) of avertically polarized signal. Additionally, this can allow radar to beable to pick up any cross polarized components of a radar signalreflected by the ground or other objects that exhibit cross polarizationconversions, such as complex terrain, shrubberies, trees, snow, rain,and complex targets, etc. This can allow a vehicle control system oranother system to use radar to analyze the environment more thoroughly,including measuring and analyzing a driving scene with variouspolarizations.

As discussed above, a polarization filter represents a layer of materialthat can manipulate operation of one or multiple antennas of a radarunit. In some embodiments, a polarization filter can cause a subset oftransmission antennas to transmit radar signals in a second polarizationdespite the transmission antennas having an initial design that causesthem to transmit radar signals in a first polarization without thepolarization filter. For example, when a polarization filter ispositioned on a transmission antenna configured to transmit verticallylinear polarized radar signals, the polarization filter can adjust theoutput of the transmission antenna such that the transmission antennatransmits radar signals that are differently polarized (e.g., horizontallinear polarized). Additionally, in further example embodiments, a radarunit may include one or multiple polarization filters that causetransmission antennas to transmit and reception antennas to receiveradar signals radiating at slanted polarizations at approximatelypositive and negative forty-five degrees from a horizontal plane

Some example embodiments may involve using multiple radar polarizationfilters to adjust polarizations of one or multiple antennas of a radarunit. For example, a radar unit may include a first polarization filtercoupled to a first subset of its antennas and a second polarizationfilter coupled to a second subset of its antennas. In the aboveimplementation, the first polarization filter may cause the first subsetof antennas to transmit and receive radar signals traveling in a firstpolarization (e.g., a vertical linear polarization) and the secondpolarization filter may cause the second subset of antennas to transmitand receive radar signals traveling in a second polarization (e.g., ahorizontal linear polarization). Other examples of radar units mayinvolve additional polarization filters. In further examples,polarization filters can overlap.

Some example radar units can have various configurations, including someradar units with antennas designed to transmit and/or receive radarsignals in multiple polarizations. For instance, a radar unit may havearrays of antennas designed such that each array transmits or receivesradar signals in a particular polarization, such as horizontal linearpolarization, vertical linear polarization, and slanted linearpolarizations (e.g., approximately positive and negative forty-fivedegrees from the horizontal plane). As such, these radar units that arecapable in using radar signals in multiple polarizations may stillinclude one or more polarization filters to modify the performance ofall or a subset of its antennas.

Parameters of a polarization filter can vary within examples. Forinstance, the size, thickness, and design of polarization filters maydiffer depending on the design and desired performance of the radarunits. In some examples, a radar unit may use a single polarizationfilter that covers all or a set of the antennas on the radar unit. Inother examples, a radar unit may include multiple polarization filtersthat may or may not overlap. A radar unit that includes multiplepolarization filters can have gaps in between the polarization filter orthe polarization filters may also align within any space in between.

In addition, in some embodiments, a polarization filter may be builtinto the radar unit. For instance, the polarization filter can begenerated as a portion (e.g., a layer) of the radar unit. Thepolarization filter can be the top layer positioned above antennas or asanother layer. In other embodiments, a polarization filter may beconfigurable to attach to a radar unit. For instance, the polarizationfilter may couple to the radar unit via fasteners or adhesive. As such,some example embodiments can involve polarization filters that areadjustable and can couple to and switch between different portions ofthe same radar unit.

In further examples, one or multiple polarization filters may operate inaccordance with one or multiple rotation components. For instance, aradar unit may include a rotation component that can adjust a positionor positions of one or multiple polarization filters. Adjusting theposition of a polarization filter can cause the polarization filter tomodify the polarization of antennas on the radar unit in a manner thatdependents on the current position of the polarization filter. Arotation component can adjust the position of a polarization filterusing various techniques or sources of power to perform the adjustment.

In some examples, the rotation component is a microelectromechanicalsystem (MEMS). MEMS and other potential rotation components may be madeusing microfabrication techniques. Through the use of MEMS devices, aradar unit may be able to adjust the polarization of one or more radarunits in situ. By way of example, an in situ adjustment allows the radarunit (or vehicle) to adjust the polarization of the radar unit withouthaving to physically replace the radar hardware on the vehicle.

The configuration, position, and orientation of a transmission orreception antenna as well as the underlying waveguide channel caninfluence the polarization in which the antenna transmits or receivesradar signals, the width and distance of the transmission or reception,and direction of operation of the antenna. As such, different layouts ofradar units are presented herein that depict radar units capable ofvarious types of operation, including close range, mid-range, andfar-range from a vehicle or other device. These different layouts ofradar units can include one or multiple polarization filters that adjustthe polarization of transmission as well as reception by given antennas.

In some example embodiments, the configuration of a radar unit canfurther influence the performance of antennas of the radar unit. Inparticular, a radar unit may be configured internally to additionallymodify (e.g., twist) the polarization of electromagnetic waves to anextent desired before antennas transmit the modified electromagneticwaves as desired Likewise, the radar unit may be configured to receivereflections of radar signals and internally modify (e.g., twist) thereceived signals to a polarization desired. As an example, a radar unitmay receive and twist electromagnetic waves to a desired polarization(e.g., slanted polarization).

Radar units capable of operating in multiple polarizations can helpreduce interference and jamming that can occur when multiple vehicles ordevices use radar in the same area. Interference or jamming can cause aradar unit to receive radar signals that do not accurately represent theenvironment from the perspective of the radar unit. For instance, theradar unit positioned on a vehicle may receive unwantedly receive aradar signal that was transmitted in the same range and polarization bya radar system of a different vehicle. Further, all the differenttransmissions and reflections of radar signals can produce noise thatimpacts the performance of radar units.

By way of example, if two vehicles are driving toward one another, andboth are transmitting radar signals with vertical polarization (orhorizontal polarization), each vehicle may receive some radar signalstransmitted by the other vehicle. These radar signals from the othervehicle may jam (or otherwise interfere) with the radar units of thevehicle. However, if the radar signals from the two vehicles areorthogonal to each other, then the signals will much less likely jam orinterfere with the other vehicle's radar.

Example radar units that can transmit and receive in more than onepolarization can potentially circumvent jamming and interference bytransmitting and receiving radar signals in polarizations that differfrom the polarization used by nearby radar systems. Likewise, a radarunit can selectively transmit and receive radar signals in one or moreof multiple polarizations (e.g., all four). The radar system may use theaccumulation of measurements from the multiple polarizations to measurethe environment. Thus, one or more radar units may be able to image afield of view of the radar unit in one or more polarizations.

Further, a radar unit operating in multiple polarizations can enablefurther analysis of an environment. For instance, the radar system candetect water (e.g., puddles and/or weather conditions) positioned on ornear the roadway based on radar measurements in multiple polarizations.Because water has polarization-specific reflection properties, changingpolarizations may enhance the ability to detect water on a roadway. Avehicle control system can use enhanced detection from differentpolarizations to avoid flooded roadways or otherwise navigate aroundenvironments unfit for navigation. Likewise, measurements of radarsignals in multiple polarizations can assist in detecting metallictraffic signs, such as stop signs and street signs.

In some examples, polarimetric measurements can assist with decomposingcomplex RF reflective objects (e.g., cars, road signs) in theenvironment into canonical scattering components, such as plates, edges,cylinders, and trihedrals, etc. For example, the radar signalsreflecting off the edges of the metallic traffic signs in multiplepolarizations can assist the radar system detect the location andestimate the boundaries of a sign. As a result, the measurements canhelp form a rich and discriminative feature space that can potentiallybe used for target classification and object identification. Further, inaddition to the multi-look nature of polarimetric measurements, a systemmay use the measurements to characterize the polarimetric spectrum oftargets and potentially provide classification capabilities. Forinstance, the system may identify traffic signs based on detectedshapes, road barriers, other vehicles, pedestrians, and other featureswithin an environment using radar measurements and analysis.

The following detailed description may be used with an apparatus havingone or multiple antenna arrays that may take the form of a single-inputsingle-output single-input, multiple-output (SIMO), multiple-inputsingle-output (MISO), multiple-input multiple-output (MIMO), and/orsynthetic aperture radar (SAR) radar antenna architecture.

In some embodiments, radar antenna architecture may include a pluralityof “dual open-ended waveguide” (DOEWG) antennas. In some examples, theterm “DOEWG” may refer to a short section of a horizontal waveguidechannel plus a vertical channel that splits into two parts, where eachof the two parts of the vertical channel includes an output portconfigured to radiate at least a portion of electromagnetic waves thatenter the antenna. Additionally, a plurality of DOEWG antennas may bearranged into an antenna array. However, this technology is not limitedto DOEWG antennas, other antennas may be used within the context of thepresent disclosure as well.

An example antenna architecture may comprise, for example, multiplemetal layers (e.g., aluminum plates) that can be machined with computernumerical control (CNC), aligned properly, and joined together. Thefirst metal layer may include a first half of an input waveguidechannel, where the first half of the first waveguide channel includes aninput port that may be configured to receive electromagnetic waves(e.g., 77 GHz millimeter waves) into the first waveguide channel. Thefirst metal layer may also include a first half of a plurality ofwave-dividing channels. The plurality of wave-dividing channels maycomprise a network of channels that branch out from the input waveguidechannel and that may be configured to receive the electromagnetic wavesfrom the input waveguide channel, divide the electromagnetic waves intoa plurality of portions of electromagnetic waves (i.e., power dividers),and propagate respective portions of electromagnetic waves to respectivewave-radiating channels of a plurality of wave-radiating channels.

Some example automotive radar systems may be configured to operate withfrequencies in the IEEE W band (75-110 Gigahertz (GHz)) and/or the NATOM band (60-100 GHz). In one example, the present system may operate atan electromagnetic wave frequency of 77 GHz, which corresponds tomillimeter (mm) waves having an electromagnetic wavelength (e.g., 3.9 mmfor 77 GHz). These radar systems may use antennas that can focus theradiated energy into beams in order to enable the radar system tomeasure an environment with high accuracy, such as the surroundingenvironment around an autonomous vehicle. Such antennas may be compact,efficient (i.e., there should be little 77 GHz energy lost to heat inthe antenna, or reflected back into the transmitter electronics), andinexpensive and easy to manufacture.

In some example embodiments, a polarization filter may be disposedbetween two layers of the antenna. One of the two layers may include anarray of waveguide antenna elements (e.g., waveguides of DOEWG antennas)used for radiating or receiving signals. The other layer may includewaveguide output ports (i.e., ports between the polarization filter andthe surrounding environment).

The polarization filter may be positioned such that the roundedrectangular polarization-modification channels are positioned withrespect to the waveguide antenna elements and/or the waveguide outputports (e.g., rotated at an angle between 44 and 46 degrees with respectto the waveguide antenna elements and at an angle between 44 and 46degrees with respect to the waveguide output ports).

The waveguide antenna elements and/or the waveguide output ports may berectangular in shape, in some embodiments. In alternate embodiments, thewaveguide antenna elements and/or the waveguide output ports may becircular in shape. Other shapes are also possible.

The polarization filter may be fabricated using CNC machining ormetal-plated plastic molding, in various embodiments. The polarizationfilter could be fabricated of metal and/or dielectric, in variousexample embodiments.

The rounded rectangular channels may serve as resonant chambers that canalter the polarization of incoming electromagnetic waves. For example,high energy leakage from one polarization to another polarization (e.g.,from a horizontal TE₁₀ polarization to a vertical TE₁₀ polarization) mayoccur within the chamber. Unlike alternative methods of changingpolarization in waveguides that make use of physical twists in awaveguide occurring over a many wavelength distance, the thickness ofthe polarization filter can be less than a wavelength (e.g., between ahalf and a whole wavelength of corresponding input electromagneticwaves) while still achieving sufficient polarization conversion. Therounded rectangular polarization-modification channels may also bedesigned such that evanescent waveguide modes emanating from the channeldie out sufficiently quickly as they propagate away from the channel.Because of both of these factors, less energy loss may occur during thepolarization conversion, resulting in increased energy efficiency whencompared with alternate methods of rotating/changing polarization.

In some examples, a radar system may include one or more radar unitsconfigured to adjust the polarization of radar signals. Particularly, aradar unit within the system may be configured to operate as a DOEWGthat receives an electromagnetic wave input from a feed guide anddivides the electromagnetic waves into multiple channels. The radar unitmay further include a configuration that can receive the divided andpre-twisted electromagnetic wave from the neck of the feed waveguide andprovide additional twisting (or otherwise modification) of the dividedelectromagnetic waves to one or multiple desired polarizations withinchannels. For instance, the additional twisting may causeelectromagnetic waves to adjust from horizontal linear polarization to aslanted polarization.

As such, the radar unit may include a configuration that allows asufficient propagation path to stabilize the twisted electromagneticwaves such that all (or a portion) of the parasitic evanescent wavescease to exist and the wanted propagating electromagnetic waves survivein the desired twisted angle (i.e., at the desired polarization). Insome examples, the radar unit may further include an impedance match tofree space at the end of the guide in order to assist with radiating theelectromagnetic waves as radar signals into the environment.Additionally, since twisting electromagnetic waves may occur in the sizeof radar units capable of attaching to vehicles, the configurationallowing twisting of the electromagnetic waves may be constructed usingthe CNC machining process. Further, the twisted configuration may beincluded in various types of radar units, such as radar units configuredwith different arrays of antennas. For example, a radar unit thatinternally twists electromagnetic waves to a desired polarization mayinclude a one by ten (1×10) radiating element array.

Based on the shape and the materials of the correspondingpolarization-modification channels and waveguides, the distribution ofpropagating energy can vary at different locations within the antenna,for example. The shape and the materials of thepolarization-modification channels and waveguides define the boundaryconditions for the electromagnetic energy. Boundary conditions are knownconditions for the electromagnetic energy at the edges of thepolarization-modification channels and waveguides. For example, in ametallic waveguide, assuming the polarization-modification channel andwaveguide walls are nearly perfectly conducting (i.e., the waveguidewalls can be approximated as perfect electric conductors—PECs), theboundary conditions specify that there is no tangentially (i.e., in theplane of the waveguide wall) directed electric field at any of the wallsides. Once the boundary conditions are known, Maxwell's Equations canbe used to determine how electromagnetic energy propagates through thepolarization-modification channels and waveguides.

Maxwell's Equations may define several modes of operation for any givenpolarization-modification channel or waveguide. Each mode has onespecific way in which electromagnetic energy can propagate through thepolarization-modification channel or waveguide. Each mode has anassociated cutoff frequency. A mode is not supported in apolarization-modification channel or waveguide if the electromagneticenergy has a frequency that is below the cutoff frequency. By properlyselecting both (i) dimensions and (ii) frequency of operation,electromagnetic energy may propagate through thepolarization-modification channels and waveguides in specific modes. Thepolarization-modification channels and/or the waveguides can be designedso only one propagation mode is supported at the design frequency.

There are four main types of waveguide propagation modes: TransverseElectric (TE) modes, Transverse Magnetic (TM) modes, TransverseElectromagnetic (TEM) modes, and Hybrid modes. In TE modes, theelectromagnetic energy has no electric field in the direction of theelectromagnetic energy propagation. In TM modes, the electromagneticenergy has no magnetic field in the direction of the electromagneticenergy propagation. In TEM modes, the electromagnetic energy has noelectric or magnetic field in the direction of the electromagneticenergy propagation. In Hybrid modes, the electromagnetic energy has someof both electric field and magnetic field the direction of theelectromagnetic energy propagation.

TE, TM, and TEM modes can be further specified using two suffix numbersthat correspond to two directions orthogonal to the direction ofpropagation, such as a width direction and a height direction. Anon-zero suffix number indicates the respective number ofhalf-wavelengths of the electromagnetic energy equal to the width andheight of the respective polarization-modification channel or waveguide(e.g., assuming a rectangular waveguide). However, a suffix number ofzero indicates that there is no variation of the field with respect tothat direction. For example, a TE₁₀ mode indicates thepolarization-modification channel or waveguide is half-wavelength inwidth and there is no field variation in the height direction.Typically, when the suffix number is equal to zero, the dimension of thewaveguide in the respective direction is less than one-half of awavelength. In another example, a TE₂₁ mode indicates the waveguide isone wavelength in width (i.e., two half wavelengths) and one halfwavelength in height.

When operating a waveguide in a TE mode, the suffix numbers alsoindicate the number of field-maximums along the respective direction ofthe waveguide. For example, a TE₁₀ mode indicates that the waveguide hasone electric field maximum in the width direction and zero maxima in theheight direction. In another example, a TE₂₁ mode indicates that thewaveguide has two electric field maxima in the width direction and onemaximum in the height direction.

The antennas may be used on a transmit side, a receive side, or bothtransmit and receive sides of a radar system. Further, the addition of apolarization filter can allow for antennas with different nativepolarization orientations to communicate with one another using radiocommunications. For example, an antenna having a vertical polarizationmay transmit a signal to a receiving antenna that would natively have ahorizontal polarization. However, by including apolarization-modification layer and waveguide output ports, thereceiving antenna can receive and convert the vertically polarizedsignal, thereby enabling communication between the two components.

In some applications, the inclusion of one or multiple polarizationfilters can allow various radars within a radar system to use differentpolarizations to perform measurements. Such a capability may allowmultiple viewpoints (e.g., one of horizontally polarized electromagneticenergy and one of vertically polarized electromagnetic energy) of asingle scene. For example, certain types of inclement weather (e.g.,snow, rain, sleet, and hail) may adversely affect radar signaling. Theuse of multiple polarizations could reduce such an adverse effect.

Additionally or alternatively, different radars using differentpolarizations may prevent interference between different radars in theradar system. For example, the radar system may be configured tointerrogate (i.e., transmit and/or receive radar signals) in a directionnormal to the direction of travel of an autonomous vehicle via thesynthetic aperture radar (SAR) functionality. Thus, the radar system maybe able to determine information about roadside objects that the vehiclepasses. In some examples, this information may be two dimensional (e.g.,distances various objects are from the roadside). In other examples,this information may be three dimensional (e.g., a point cloud ofvarious portions of detected objects). Thus, the vehicle may be able to“map” the side of the road as it drives along, for example.

If two autonomous vehicles are using analogous radar systems tointerrogate the environment (e.g., using the SAR technique describedabove), it could also be useful for those autonomous vehicles to usedifferent polarizations (e.g., orthogonal polarizations) to do theinterrogation, thereby preventing interference. Additionally, a singlevehicle may operate two radars units having orthogonal polarizations sothat each radar unit does not interfere with the other radar unit. Thus,without having to redesign radar units, polarization filters can causeradar units to operate in different polarizations.

In some embodiments, multiple polarization filters could be cascadedtogether. This could increase the bandwidth of frequencies over whicheffective polarization conversion can occur using the correspondingantenna. Further, various combinations of cascaded polarization filtersand various dimensions of the rounded rectangular polarization channelswithin the cascaded polarization-modification layers could serve as afrequency filtering mechanism. Thus, the associated antennas couldselect specific polarizations within specific frequency bands over whichto perform measurements, thereby introducing an additional method ofreducing interference and providing additional radar channels for use byvarious different radar components in a radar system.

Referring now to the figures, FIG. 1 illustrates polarization filter100, which includes pegs 102, through-holes 104, andpolarization-modification channel 106. Polarization filter 100 can haveother configurations and may be generated in various types of materials,such as metal fabricated using CNC. Further, polarization filter 100 canbe a component of a radar unit, but can have other applications as well.Additionally, polarization filter 100 may be an example of a singlepolarization unit that can be replicated multiple times over a pluralityof antennas in order to rotate the polarization transmitted by saidantenna.

Multiple polarization filter 100 could further be cascaded to allow foradditional rotation of polarization. Further, the cascaded polarizationfilters could permit an increased bandwidth of frequencies over whichpolarization conversion can occur.

Pegs 102 can enable polarization filter 100 to connect to and/or alignwith other components. For example, pegs 102 may align polarizationfilter 100 with alignment holes on other radar components, such aswaveguides or antennas (e.g., a horn antenna as illustrated in FIG. 4).In alternate embodiments, there may be more than two pegs 102, fewerthan two pegs 102, or no pegs 102 at all.

Through-holes 104 can perform similar tasks to those performed by pegs102 (e.g., connect and/or align polarization filter 100 with othercomponents). For example, in some embodiments, through-holes 104 may bethreaded, allowing through-holes 104 to be engaged by fasteners toconnect polarization filter 100 to other radar components. Asillustrated in FIG. 1, there are four through-holes 104. In alternateembodiments, there may be more than four through-holes 104, fewer thanfour through-holes 104, or no through-holes 104 at all.

Polarization-modification channel 106 represents a portion ofpolarization filter 100 in which electromagnetic waves undergo amodification of polarization. The thickness and possibly otherparameters of the polarization-modification channel 106, and thereforein some embodiments the thickness of the main body of the entirepolarization filter 100, may be defined based on one or more wavelengthsexpected to undergo polarization modification using polarization filter100 (e.g., if polarization filter 100 is being used in radarapplications that utilize 77 GHz electromagnetic waves, the thickness ofpolarization filter 100 could be around 3.9 mm, or about onewavelength).

An angle of polarization-modification channel 106 relative to one ormore mounting points (e.g., pegs 102 or the through-holes 104) maydefine how much polarization rotation occurs when polarization filter100 acts on an electromagnetic wave. In the example embodimentillustrated in FIG. 1, polarization-modification channel 106 is at a45-degree angle relative to a line between pegs 102. Therefore, if awaveguide aligns with pegs 102 for example, electromagnetic wavespassing through polarization-modification channel 106 will undergo apolarization rotation of 45 degrees. This results in the antennatransmitting or receiving radar signals that radiate at a differentpolarization than the antenna was originally configured for. Otherangles are also possible (e.g., 44 degrees or 46 degrees).

In some embodiments, polarization-modification channel 106 could befilled or partially filled with a material other than air. For example,a dielectric could be used to fill polarization-modification channel 106to alter a resonant wavelength inside of polarization-modificationchannel 106, thereby altering an input wavelength range over whichpolarization-modification can occur using polarization filter 100.

In some embodiments, the shape of polarization-modification channel 106could be changed. For example, polarization-modification channel 106could be circular or substantially circular, allowing for an alignmentof polarization filter 100 with circular waveguides. In the embodimentillustrated in FIG. 1, polarization-modification channel 106 has a shapeof a rounded rectangle. Geometrically, such a shape can be defined asthe shape obtained by taking the convex hull of four equal circles of agiven radius and placing the centers of the four circles at the fourcorners of a rectangle having a first side length and a second sidelength.

FIG. 2 illustrates polarization filter 100 and waveguide 202. As shown,FIG. 2 includes polarization filter 100 illustrated in FIG. 1 (includingpegs 102, through-holes 104, and polarization-modification channel 106),as well as a rounded rectangular waveguide 202 forming system 200. Assuch, rectangular waveguide 202 and polarization filter 100 may havefeatures sized to accommodate electromagnetic waves having a frequencyof 77 GHz, for example. Other frequencies inside and outside of theradio spectrum are also possible.

As illustrated in FIG. 2, a long end of a port on waveguide 202 (e.g.,the length of waveguide 202) may lie parallel to a line between pegs 102of polarization filter 100. As a result, polarization-modificationchannel 106 may couple at a 45-degree angle relative to the orientationof the port on rectangular waveguide 202 (other angles are alsopossible). This can allow the system 200 to be configured to radiateelectromagnetic waves that have a polarization that is rotated by anangle (e.g., between 44 and 46 degrees) relative to an inputpolarization at a base of waveguide 202 (e.g., a port on a side ofwaveguide 202 opposite of polarization filter 100).

In other embodiments, system 200 may receive electromagnetic waveshaving a particular polarization at polarization-modification channel106 and rotate or otherwise adjust the polarization of the acceptedelectromagnetic polarization by an angle between 44 and 46 degrees(i.e., act as a receiver rather than a transmitter). System 200 canenable communication between a component on one end (e.g., the transmitend) of a radar system to communicate with a component on a second end(e.g., a receive end) of the radar system, even if the components havedifferent inherent polarizations. For example, thepolarization-modification channel 106 could be tuned to an appropriateangle that corresponds to the difference in polarizations between thetwo components.

In alternate embodiments, rectangular waveguide 202 could instead bereplaced by a circular waveguide, an elliptical waveguide, or arectangular waveguide. In such embodiments, polarization-modificationchannel 106 may consequently be designed of a different shape (e.g.,circular, elliptical, or rectangular).

Additionally or alternatively, polarization filter 100 could be used toselect specific polarizations or frequencies through filtering. Suchfiltering considerations could also lead to variations in the shape,size, or filling material used within polarization-modification channel106. In some embodiments, polarization-modification channel 106 may bedesigned to transmit, and possibly alter, electromagnetic waves havingcircular or elliptical polarization.

In addition, polarization filter 100 can act as a corrective iris on topof the rectangular waveguide. For example, if the rectangular waveguideis misshapen (e.g., one side of the rectangular waveguide is bent),polarization-modification channel 106 can have a shape that compensatesfor the shape of the rectangular waveguide.

As discussed above, system 200 may form a component of a radar antennaor a radio communication system, for example. Various other applicationsfor system 200 are also possible. In such alternate applications,dimensions of waveguide 202 or polarization filter 100 can have otherconfigurations that account for a given wavelength corresponding toelectromagnetic waves used in the respective application, for example.

FIG. 3 illustrates polarization filter 100 and waveguides 202, 302. Asillustrated, polarization filter 100 may be polarization filter 100illustrated in FIGS. 1 and 2, and waveguide 202 may be the roundedrectangular waveguide 202 illustrated in FIG. 2.

In the embodiment depicted in FIG. 3, waveguide 202 may be referred toas the lower waveguide 202, and waveguide 302 may be referred to as theupper waveguide 302. Polarization filter 100, the lower rectangularwaveguide 202, and the upper rectangular waveguide 302 can togethercomprise a system 300. As illustrated, the system 300 may be similar tothe system 200 illustrated in FIG. 2 with an addition of the upperrectangular waveguide 302 seated on or fastened to a side ofpolarization filter 100 opposite the side of polarization filter 100 towhich the lower rectangular waveguide 202 is seated or fastened.

As illustrated, the system 300 can be configured to radiateelectromagnetic waves that have a polarization rotation of 90 degrees,for example, relative to an input polarization at the base of the lowerrectangular waveguide 202. Such an arrangement could allow inputelectromagnetic waves (e.g., at a port on a side of the lowerrectangular waveguide 202 opposite of polarization filter 100) to berotated from a horizontal TE₁₀ polarization to a vertical TE₁₀polarization at the output (e.g., a port on a side of the upperrectangular waveguide 302 opposite of polarization filter 100), forexample. Other angular rotations between input and output are alsopossible.

Alternatively, the system 300 could be used to receive electromagneticwaves of a given polarization at a port of the upper rectangularwaveguide 302, and then rotate the polarization of the electromagneticwaves through an angle (e.g., an angle between 75 and 105 degrees)before emitting the electromagnetic waves having the rotatedpolarization out of a port in the base of the lower rectangularwaveguide 202.

In some embodiments, the upper waveguide 302 may represent a waveguideoutput port of a radiating antenna, for example. Further, the lowerwaveguide 202 may represent a waveguide antenna element, connected to anelectrical circuit within a radar system for example.

In the embodiment illustrated in FIG. 3, the upper waveguide 302 and thelower waveguide 202 may be of similar shapes and sizes, but rotated inorientation with respect to one another (e.g., at an angle between 88and 92 degrees). Also, in addition to or alternatively to rotation withrespect to one another about a vertical axis, one or both of the upperwaveguide 302 and the lower waveguide 202 could be rotated with respectto an axis that lies parallel to a plane of the surface of polarizationfilter 100. In alternate embodiments, the upper waveguide 302 and thelower waveguide 202 may be different lengths, widths, heights, orshapes. Analogous to the system 200 illustrated in FIG. 2, regardless ofwhether the upper waveguide 302 and the lower waveguide 202 are the sameshape or size as one another, one or both of the upper waveguide 302 andthe lower waveguide 202 could be circular, elliptical, or rectangularwaveguides, as opposed to rounded rectangular waveguides. If therespective shapes of the upper waveguide 302 and the lower waveguide 202are not equivalent, dimensions of the respective waveguides may bealtered to accommodate the shape difference (e.g., if the lowerwaveguide 202 is a rounded rectangle and the upper waveguide 302 is arectangle, the lower waveguide 202 may be slightly longer or wider toaccommodate equivalent modes to those accommodated by the upperwaveguide 302). In still other embodiments, one or both of the upperwaveguide 302 and the lower waveguide 202 could be replaced by othercomponents (e.g., photonic components or electronic components).

FIG. 4 illustrates a waveguide 202, a unit cell of polarization filter100, and a horn antenna 404, according to example embodiments. Asillustrated, polarization filter 100 may be thepolarization-modification unit cell illustrated in FIGS. 1, 2, and 3,and waveguide 202 may be waveguide 202 illustrated in FIGS. 2 and 3.Polarization filter 100, waveguide 202, and the horn antenna 404 cantogether comprise a system 400. Also included in the system 400illustrated in FIG. 4, are two fastening plates 402 used to connect theother components of the system 400 (i.e., waveguide 202, polarizationfilter 100, and the horn antenna 404) to one another. As illustrated,the system 400 may be similar to the system 200 illustrated in FIG. 2with an addition of the horn antenna 404 fastened to a side ofpolarization filter 100 opposite the side to which waveguide 202 isfastened.

As illustrated in FIG. 4, polarization filter 100 may be removablyconnected to the horn antenna 404 and waveguide 202 using the fasteningplates 402. The fastening plates 402, for example, may be directlyconnected to the horn antenna 404 and waveguide 202, respectively, in asemi-permanent fashion (e.g., welded to the horn antenna 404 andwaveguide 202). The fastening plates 402 may then be attached to oneanother, polarization filter 100, or both, using bolts, as illustrated,for example. The bolts may replace pegs 102 illustrated in FIG. 1.Alternatively, the bolts may be threaded through threaded ports orthrough-holes defined within pegs 102 or through one or more otherthrough-holes, such as the through-holes 104 illustrated in FIG. 1.Additionally, the system 400 may employ nuts, washers, or both to securethe fastening plates 402 to one another or to polarization filter 100.

In alternate embodiments, the use of fastening plates 402 within thesystem 400 may be superfluous. For example, the horn antenna 404,waveguide 202 or both may be directly connected (e.g., welded orfastened) to a portion of polarization filter 100, thereby obviating aneed to use fastening plates 402. In still other embodiments, thefastening plates 402 may be shaped differently (e.g., rectangular ratherthan circular).

The horn antenna 404 represents a radiating element of the system 400illustrated in FIG. 4. The horn antenna 404 may be an alternateradiating element used in place of the upper waveguide 302 illustratedin FIG. 3. Potential advantages of using the horn antenna 404 couldinclude improved directivity, bandwidth, and standing wave ratio (SWR)when compared with alternate antenna radiating elements such as theupper waveguide 302 illustrated in FIG. 3. In alternate embodiments, thehorn antenna 404 may have an alternate shape (e.g., a sectoral horn, aconical horn, an exponential horn, a corrugated horn, a dual-modeconical horn, a diagonal horn, a ridged horn, a septum horn, or anaperture-limited horn, as opposed to a pyramidal horn) or be sized in adifferent way (e.g., a width dimension of an output port of the hornantenna 404 is larger than a length dimension of the output port of thehorn antenna 404). Such changes to the horn antenna 404 may be made suchthat the horn antenna 404 radiates electromagnetic waves of differentfrequencies more efficiently or corresponding to differentpolarizations, for example. In alternate embodiments, besides thoseillustrated in FIGS. 3 and 4, other radiating elements are also possible(e.g., bowtie antennas or corner reflector antennas).

The horn antenna 404 may, analogous to the upper waveguide 302illustrated in FIG. 3, radiate electromagnetic waves that have a rotatedpolarization from a polarization that was input to a port at a base ofwaveguide 202. For example, the polarization could be rotated between 88and 92 degrees (e.g., from roughly a horizontal TE₁₀ polarization toroughly a vertical TE₁₀ polarization, or vice versa).

FIG. 5 illustrates a unit cell of another polarization-modification 500,according to example embodiments. Similar to the embodiment illustratedin FIG. 1, the polarization-modification unit cell 500 illustrated inFIG. 5 includes pegs 502, through-holes 504, and apolarization-modification channel 506. The polarization-modificationunit cell 500 may be a plate of metal, fabricated using CNC, forexample, with other components defined therein (e.g., thepolarization-modification channel 506) and/or thereon (e.g., the twopegs 502). While the polarization-modification unit cell 500 may be acomponent of an antenna or a radar system, the polarization-modificationunit cell 500 may be used in various other applications.

Multiple polarization-modification unit cells 500 could further becascaded to allow for additional rotation of polarization. For example,nine cascaded polarization-modification unit cells, each being similarto polarization-modification unit cell 500, could each be cascaded oneafter another. Each of the nine cascaded polarization-modification unitcells could have successive polarization-modification channels 506 thatare offset 10 degrees from the polarization-modification channels 506 ofadjacent polarization-modification unit cells. In this way, the ninecascaded polarization-modification unit cells could rotate polarizationof input electromagnetic waves to polarization of output electromagneticwaves by 90 degrees. Further, the cascaded polarization-modificationunit cells could permit an increased bandwidth of frequencies over whichpolarization conversion can occur. For example, a set of cascadedpolarization-modification unit cells could act as a broadband (in termsof accepted electromagnetic frequencies) polarization rotating device.In some embodiments, such a device could be capable of rotating anyelectromagnetic wave having a frequency within the “E-band” (i.e., 60-90GHz), for example.

Similar to the embodiment illustrated in FIG. 1, pegs 502 can beconfigured to allow the polarization-modification unit cell 500 toconnect to and/or align with other components. For example, pegs 502 mayalign the polarization-modification unit cell 500 with alignment holeson other radar components, such as waveguides or antennas (e.g., thehorn antenna 404 illustrated in FIG. 4). In alternate embodiments, theremay be more than two pegs 502, fewer than two pegs 502, or no pegs 502at all.

Also analogous to the embodiment illustrated in FIG. 1, through-holes504 can perform similar tasks to those performed by pegs 502 (e.g.,connect and/or align the polarization-modification unit cell 500 withother components). For example, in some embodiments, through-holes 504may be threaded, allowing through-holes 504 to be engaged by fastenersto connect the polarization-modification unit cell 500 to other radarcomponents. As illustrated in FIG. 5, there are four through-holes 504.In alternate embodiments, there may be more than four through-holes 504,fewer than four through-holes 504, or no through-holes 504 at all.

The polarization-modification channel 506, in this embodiment, is thecomponent of the polarization-modification unit cell 500 in whichelectromagnetic waves undergo a rotation of polarization. The thicknessof the polarization-modification channel 506, and therefore, in someembodiments, the thickness of the main body of thepolarization-modification unit cell 500, may be defined based on one ormore wavelengths (or fractions of a wavelength) expected to undergopolarization-modification using the polarization-modification unit cell500 (e.g., if the polarization-modification unit cell 500 is being usedin radar applications that utilize 77 GHz electromagnetic waves, thethickness of the polarization-modification unit cell 500 could be around3.9 mm, or about one wavelength).

An angle of the polarization-modification channel 506 relative to one ormore mounting points (e.g., pegs 502 or through-holes 504) may definehow much polarization-modification occurs when thepolarization-modification unit cell 500 acts on an electromagnetic wave.Unlike the embodiment illustrated in FIG. 1, however, thepolarization-modification channel 506 illustrated in FIG. 5 is rotatedbetween 10 and 15 degrees relative to a line that is perpendicular to aline between the two pegs 502. Other angles are also possible inalternate embodiments. As stated above, smaller angles may increase thebandwidth of frequencies of incoming electromagnetic waves over whichthe polarization-modification channel 506 can effectively rotatepolarization, especially when multiple polarization-modification unitcells 500 are cascaded.

In some embodiments, the polarization-modification channel 506 could befilled or partially filled with a material other than air. For example,a dielectric could be used to fill the polarization-modification channel506 to alter a resonant wavelength inside of thepolarization-modification channel 506, thereby altering an inputwavelength range over which polarization rotation can occur using thepolarization-modification unit cell 500.

Still further, in some alternate embodiments, the shape of thepolarization-modification channel 506 could be changed. For example, thepolarization-modification channel 506 could be circular or substantiallycircular, allowing for an alignment of the polarization-modificationunit cell 500 with circular waveguides. In the embodiment illustrated inFIG. 5, the polarization-modification channel 506 has a shape of arounded rectangle (i.e., the shape is substantially rectangular).Geometrically, such a shape can be defined as the shape obtained bytaking the convex hull of four equal circles of a given radius andplacing the centers of the four circles at the four corners of arectangle having a first side length and a second side length.

Additionally or alternatively, some embodiments may influence two ormore degenerate modes to form a single circularly polarized wave. Insuch embodiments, it may be possible for the unit cell to launch orradiate a circularly polarized wave upon receiving only linearlypolarized waves as inputs. For example, this may occur in embodimentswhere the shape of the polarization-modification channel is an ellipsehaving low eccentricity, a trapezoid, or a rectangle having nearly equalside lengths.

FIG. 6 illustrates a unit cell of another polarization-modification 500and two waveguides 602/604, according to example embodiments. Asillustrated, the polarization-modification unit cell 500 may be thepolarization-modification unit cell 500 illustrated in FIG. 5. In theembodiment of FIG. 6, the waveguides 602, 604 may respectively bereferred to as the upper waveguide 604 and the lower waveguide 602. Thepolarization-modification unit cell 500, the lower waveguide 602, andthe upper waveguide 604 can together comprise a system 600. Asillustrated, the system 600 may be similar to the system 300 illustratedin FIG. 3. The primary difference, however, is the orientation of theupper waveguide 604 with respect to the polarization-modification unitcell 500 and the lower waveguide 602. As illustrated in FIG. 6, theupper waveguide 604 is angularly offset about a vertical axis from thelower waveguide 602 by roughly 30 degrees (as opposed to roughly 90degrees, as illustrated in FIG. 3). As described above with regards toother systems and waveguides, the system 600 illustrated in FIG. 6 couldbe cascaded multiple times to achieve various other angles ofpolarization rotation (e.g., three instances of the system 600 could becascaded to rotate polarization by roughly 90 degrees).

As described above, the system 600 can be configured to radiateelectromagnetic waves that have polarization rotation of 30 degrees, forexample, relative to an input polarization at the base of the lowerrectangular waveguide 602. Such an arrangement could allow inputelectromagnetic waves (e.g., at a port on a side of the lower waveguide602 opposite of polarization filter 100) to be rotated from one TE₁₀polarization to another TE₁₀ polarization at the output (e.g., a port ona side of the upper waveguide 604 opposite of polarization filter 100),for example. Other angular rotations between input and output are alsopossible.

Alternatively, the system 600 could be used to receive electromagneticwaves of a given polarization at a port of the upper waveguide 604, andthen rotate the polarization of the electromagnetic waves through anangle (e.g., an angle between 25 and 35 degrees) before emitting theelectromagnetic waves having the rotated polarization out of a port inthe base of the lower waveguide 602.

In some embodiments, the upper waveguide 604 may represent a waveguideoutput port of a radiating antenna, for example. Further, the lowerwaveguide 602 may represent a waveguide antenna element, connected to anelectrical circuit or a feed waveguide within a radar system forexample.

In the embodiment illustrated in FIG. 6, the upper waveguide 604 and thelower waveguide 602 may be of similar shapes and sizes, but rotated inorientation with respect to one another (e.g., at an angle between 25and 35 degrees). Also, in addition to or alternatively to rotation withrespect to one another about a vertical axis, one or both of the upperwaveguide 604 and the lower waveguide 602 could be rotated with respectto an axis that lies parallel to a plane of the surface of thepolarization-modification unit cell 500. In alternate embodiments, theupper waveguide 604 and the lower waveguide 602 may be differentlengths, widths, heights, or shapes. Additionally, regardless of whetherthe upper waveguide 604 and the lower waveguide 602 are the same shapeor size as one another, one or both of the upper waveguide 604 and thelower waveguide 602 could be circular, elliptical, or rectangularwaveguides, as opposed to rounded rectangular waveguides. If therespective shapes of the upper waveguide 604 and the lower waveguide 602are not equivalent, dimensions of the respective waveguides may bealtered to accommodate the shape difference (e.g., if the lowerwaveguide 602 is a rounded rectangle and the upper waveguide 604 is arectangle, the lower waveguide 602 may be slightly longer or wider toaccommodate equivalent modes to those accommodated by the upperwaveguide 604).

FIG. 7 illustrates a polarization filter 700, according to exampleembodiments. The polarization filter 700 illustrated in FIG. 7 hasmultiple polarization-modification channels 702 defined therein. Thepolarization-modification channels 702 may form an array ofpolarization-modification channels. Each polarization-modificationchannels 702 may be similar to the polarization-modification channel 106illustrated in FIG. 1. Further, the polarization filter 700 may bedesigned for used with an antenna (e.g., a radar antenna), such as theantenna 900 illustrated in FIG. 9.

As illustrated, the polarization-modification channels 702 may bedefined in an array-like fashion within the polarization filter 700. Thepolarization-modification channels 702 may further be at an anglebetween 44 and 46 degrees (e.g., 45 degrees) relative to an orientationof the polarization filter 700, for example. Other angles are alsopossible. Further, while the embodiment illustrated in FIG. 7 depictseach of the polarization-modification channels 702 as having a similarorientation with respect to the polarization filter 700, this need notbe the case. In additional embodiments, the polarization-modificationchannels 702 could be irregularly arranged or have different angles thanone another. In some devices or systems, the polarization rotation thatmay occur using the polarization-modification layer 700 may not beisotropic for all regions within the device/system.

As illustrated in FIG. 7, the polarization-modification channels 702have the shape of a stadium. Geometrically, a stadium (i.e., adisco-rectangle or another partially rounded shape) is defined as arectangle with semicircles at a pair of opposite sides. However, thepolarization-modification channels 702 may have various alternativeshapes (e.g., an ellipse, a circle, a rounded rectangle, or a rectangle)or sizes (e.g., different radii, lengths, widths, etc.). Further, thepolarization-modification channels 702 may not be the same size or shapeas one another. As with the angle of rotation relative to thepolarization-modification layer 700, the polarization-modificationchannels 702 may have varied shapes and sizes, perhaps spacedirregularly about the polarization-modification layer 700. Stillfurther, the thickness of the polarization-modification layer 700 mayvary among embodiments. For example, the thickness of thepolarization-modification layer 700 may be between a half wavelength anda whole wavelength of the associated electromagnetic waves for which thepolarization-modification layer 700 is designed (e.g., between 1.45 and3.9 mm for a polarization-modification layer 700 designed to rotatepolarization of incoming electromagnetic waves having an associatedfrequency of 77 GHz).

In some examples, the polarization-modification layer 700 may alsoinclude one or multiple resonant cavities. For instance, a resonantcavity may be located on a bottom side of the polarization-modificationlayer 700 and can function to match an impedance of thepolarization-modification layer 700 to an impedance of the antenna towhich the polarization-modification layer 700 is coupled.

Additionally or alternatively, the polarization-modification layer 700could be used to select specific polarizations or frequencies throughfiltering. Such filtering considerations could also lead to variationsin the shape, size, or filling material used within thepolarization-modification channels 702. In other embodiments, thepolarization-modification channels 702 may be designed to transmit, andpossibly alter, electromagnetic waves having circular or ellipticalpolarization.

FIG. 8A illustrates an example wave-radiating doublet of an exampleantenna, according to example embodiments. The example antenna could beused to radiate or receive radio waves, in example embodiments. Morespecifically, FIG. 8A illustrates a cross-section of an example DOEWG800. The DOEWG 800 may include a horizontal feed (i.e., channel), avertical feed (i.e., a doublet neck), and a wave-directing member 804.The vertical feed may be configured to couple energy from the horizontalfeed to two output ports 802, each of which is configured to radiate atleast a portion of electromagnetic waves out of the DOEWG 800. In someembodiments, the farthest DOEWG from the input port may include abackstop at location 806. DOEWGs that come before the last DOEWG maysimply be open at location 806 and electromagnetic waves may propagatethrough that location 806 to subsequent DOEWGs. For example, a pluralityof DOEWGs may be connected in series where the horizontal feed is commonacross the plurality of DOEWGs (as shown in FIG. 8B). FIG. 8A showsvarious parameters that may be adjusted to tune the amplitude and/orphase of an electromagnetic signal that couples into the radiatingelement.

In order to tune a DOEWG such as DOEWG 800, the vertical feed width,vfeed_a, and various dimensions of the step 804 (e.g., dw, dx, and dz1)may be tuned to achieve different fractions of radiated energy out theDOEWG 800. The step 804 may also be referred to as a reflectingcomponent as it reflects a portion of the electromagnetic waves thatpropagate down the horizontal feed into the vertical feed. Further, insome examples, the height dz1 of the reflecting component may benegative. That is, the step 804 may extend below the bottom of thehorizontal feed. Similar tuning mechanisms may be used to tune theoffset feed as well. For example, the offset feed may include any of thevertical feed width, vfeed_a, and various dimensions of the step (e.g.,dw, dx, and dz1) as discussed with respect to the radiating element.

In some examples, each output port 802 of the DOEWG 800 may have anassociated phase and amplitude. In order to achieve the desired phaseand amplitude for each output port 802, various geometrical componentsmay be adjusted. As previously discussed, the step (reflectingcomponent) 704 may direct a portion of the electromagnetic wave throughthe vertical feed. In order to adjust amplitude associated with eachoutput port 802 of a respective DOEWG 800, a height associated with eachoutput port 802 may be adjusted. Further, the height associated witheach output port 802 could be the height or the depth of this feedsection of output port 802.

As shown in FIG. 8A, height dz2 and height dz3 may be adjusted tocontrol the amplitude with respect to the two output ports 802. In someembodiments, such as the embodiment of FIG. 9, the two output ports 802(given reference numeral 902 in FIG. 9) may instead be referred to aswaveguide antenna elements (e.g., the waveguide antenna elements 902illustrated in FIG. 9) as they are shaped like and may function aswaveguides and further may serve to radiate or receive electromagneticwaves. The adjustments to height dz2 and height dz3 may alter thephysical dimensions of the doublet neck (e.g., vertical feed of FIG.8A). The doublet neck may have dimensions based on the height dz2 andheight dz3. Thus, as the height dz2 and height dz3 are altered forvarious doublets, the dimensions of the doublet neck (i.e., the heightof at least one side of the doublet neck) may change. In one example,because height dz2 is greater than height dz3, the output port 802associated with (i.e., located adjacent to) height dz2 may radiate witha greater amplitude than the amplitude of the signal radiated by theoutput port 802 associated with height dz3.

Further, in order to adjust the phase associated with each output port802, a step may be introduced for each output port 802. The step in theheight may cause a phase of a signal radiated by the output port 802associated with the respective step to change. Thus, by controlling boththe height and the respective step associated with each output port 802,both the amplitude and the phase of a signal transmitted by the outputport 802 may be controlled. In various embodiments, the steps may takevarious forms, such as a combination of up-steps and down-steps.Additionally, the number of steps may be increased or decreased tocontrol the phase.

The above-mentioned adjustments to the geometry may also be used toadjust a geometry of the offset feed where it connects to the waveguide.For example, heights, widths, and steps may be adjusted or added to theoffset feed in order to adjust the radiation properties of the system.An impedance match, phase control, and/or amplitude control may beimplemented by adjusting the geometry of the offset feed.

FIG. 8B illustrates an example offset feed waveguide portion 856 of anexample antenna 850, according to example embodiments. As shown in FIG.8B, a waveguide 854 may include a plurality of radiating elements (shownas 852A-852E) and an offset feed 856. Although the plurality ofradiating elements is shown as doublets in FIG. 8B, other radiatingstructures may be use as well. For example, singlets, and any otherradiating structure that can be coupled to a waveguide may be used aswell.

The waveguide 854 may include various shapes and structures configuredto direct electromagnetic power to the various radiating elements 852A-Eof waveguide 854. A portion of electromagnetic waves propagating throughwaveguide 854 may be divided and directed by various recessedwave-directing member and raised wave-directing members. The pattern ofwave-directing members shown in FIG. 8B is one example for thewave-directing members. Based on the specific implementation, thewave-directing members may have different sizes, shapes, and locations.Additionally, the waveguide may be designed to have the waveguide ends860A and 860B to be tuned shorts. For example, the geometry of the endsof the waveguides may be adjusted so the waveguide ends 860A and 860Bact as tuned shorts.

At each junction of one of the respective radiating elements 852A-E ofwaveguide 854, the junction may be considered a two-way power divider. Apercentage of the electromagnetic power may couple into the neck of therespective radiating elements 852A-E and the remaining electromagneticpower may continue to propagate down the waveguide. By adjusting thevarious parameters (e.g., neck width, heights, and steps) of eachrespective radiating element 852A-E, the respective percentage of theelectromagnetic power may be controlled. Thus, the geometry of eachrespective radiating element 852A-E may be controlled in order toachieve the desired power taper. Thus, by adjusting the geometry of eachof the offset feed and each respective radiating element 852A-E, thedesired power taper for a respective waveguide and its associatedradiating elements may be achieved.

Electromagnetic energy may be injected into the waveguide 854 via thewaveguide feed 856. The waveguide feed 856 may be a port (e.g., athrough-hole) in a bottom metal layer, in some embodiments. Anelectromagnetic signal may be coupled from outside the antenna unit intothe waveguide 854 through the waveguide feed 856. The electromagneticsignal may come from a component located outside the antenna unit, suchas a printed circuit board, another waveguide, or other signal source.In some examples, the waveguide feed 856 may be coupled to anotherdividing network of waveguides (such as illustrated in FIGS. 9 and 10).

In some examples, the present system may operate in one of two modes. Inthe first mode, the system may receive electromagnetic energy from asource for transmission (i.e., the system may operate as a transmissionantenna). In the second mode, the system may receive electromagneticenergy from outside of the system for processing (i.e., the system mayoperate as a reception antenna). In the first mode, the system mayreceive electromagnetic energy at a waveguide feed, divide theelectromagnetic energy for transmission by a plurality of radiatingelements, and radiate the divided electromagnetic energy by theradiating elements. In the second mode, the system may receiveelectromagnetic energy at the plurality of radiating elements, combinethe received electromagnetic energy, and couple the combinedelectromagnetic energy out of system for further processing.

It should be understood that other shapes and dimensions of thewaveguide channels, portions of the waveguide channels, sides of thewaveguide channels, wave-directing members, and the like are possible aswell. In some embodiments, a rectangular shape of waveguide channels maybe highly convenient to manufacture, though other methods known or notyet known may be implemented to manufacture waveguide channels withequal or even greater convenience.

FIG. 9 illustrates an array of waveguide antenna elements 902, accordingto example embodiments. The size and shape of the waveguide antennaelements 902, as well as the corresponding feed waveguides illustratedin FIG. 9, may correspond to a given electromagnetic frequency (e.g., 77GHz) and/or polarization (e.g., horizontal TE₁₀ polarization) for whichthe array of waveguide antenna elements 902 is designed to operate.Along with other components pictured, the waveguide antenna elements 902may be part of an antenna system 900. The waveguide antenna elements 902may be arranged in an array, as illustrated in FIG. 9. Further, thearray of waveguide antenna elements 902 may be arranged in a group ofindividual antennas 850 as illustrated in FIG. 8. Specifically, theembodiment illustrated in FIG. 9 includes six instances of the antenna850 illustrated in FIG. 8, resulting in a 6×10 array of waveguideantenna elements 902. Other numbers of waveguide antenna elements 902and/or antennas 850 are also possible. The antenna system 900 may be ona transmit end and/or a receive end of a radar or radio communicationsystem, for example. Further, two instances of the antenna system 900can be used in conjunction with one another to form a transmit/receivesystem (e.g., a radio communication system). Still further, the antennasystem 900 may be designed to radiate and/or receive electromagneticwaves in a TE₁₀ waveguide mode.

In addition to the waveguide antenna elements 902 arranged in a group ofantennas 850 illustrated in FIG. 9, the antenna system 900 mayadditionally include a phase adjusting section 910 and a waveguide input912. The waveguide input 912 may be connected to an electromagneticsource (e.g., a radar source), in some embodiments. The phase adjustingsection 910 may adjust a phase associated with electromagnetic wavesinput into the waveguide input 912, for example. This could allow properphase to be distributed to each of the waveguide antenna elements 902when transmitting a signal. Further, the phase adjusting section 910 maybe configured to divide power of an incoming electromagnetic wave amongmultiple feed waveguides associated with multiple instances of theantenna 850.

In some embodiments, as described above, antenna system 900 may includea series of independent antennas 850 that are connected to a commonwaveguide input 912. Instead of being independent antennas 850, theantennas 850 may function as a single antenna unit, as illustrated inFIG. 9. Whether the antenna system 900 describes independent antennas ora single antenna unit, the waveguide antenna elements 902 can serve toradiate electromagnetic waves and/or receive electromagnetic waves. Theelectromagnetic waves radiated and/or received may be transmitted downthe horizontal and vertical feeds of the corresponding waveguides, asdescribed with regard to FIG. 8.

FIG. 10 illustrates an array of waveguide antenna elements 902 and apolarization-modification layer 700, according to example embodiments.In some embodiments, the array of waveguide antenna elements 902 may bedesigned according to an industry standard (e.g., an automotive industrystandard) and the polarization-modification layer 700 may be designed insuch a way as to accommodate that industry standard. Alternatively, thearray of waveguide antenna elements 902 and the correspondingpolarization-modification layer 700 could be designed for one or morespecific applications. Collectively, the array of waveguide antennaelements 902 and the polarization-modification layer 700 may comprise anantenna 1000. In some embodiments, as in the embodiment illustrated inFIG. 10, the antenna 1000 may additionally include the phase adjustingsection 910 and/or the waveguide input 912 illustrated in FIG. 9. In theexample embodiment of FIG. 10, the thickness of thepolarization-modification layer 700 could be less than a wavelengththick (e.g., between a quarter wavelength and a whole wavelength) of theelectromagnetic waves which the antenna 1000 was designed to transmit orreceive. Other thicknesses are also possible. Further, the antenna 1000may be designed to radiate or receive electromagnetic waves in a TE₁₀waveguide mode.

In the embodiment illustrated in FIG. 10, the polarization-modificationchannels 702 defined within the polarization-modification layer 700 mayserve to rotate polarization emitted by the waveguide antenna elements902. Thus, the electromagnetic waves radiated by the antenna 1000 may beof a polarization that is rotated with respect to a polarization that isoutput by the waveguide antenna elements 902. Additionally oralternatively (e.g., if the antenna 1000 is acting as a receiver withina radar system or radio communication system), thepolarization-modification channels 702 defined within thepolarization-modification layer 700 may serve to rotate a polarizationassociated with a received electromagnetic wave prior to transmittingthe electromagnetic wave to the waveguide antenna elements 902.

As previously discussed with respect to FIG. 7, thepolarization-modification layer 700 may also include a resonant cavityas part of each of the polarization-modification channels 702. Theresonant cavity may be configured to perform impedance matching betweeneach waveguide antenna elements 902 and the respective one of thepolarization-modification channels 702 coupled to the waveguide antennaelements 902. In some radar systems, for example, a transmitter may beconfigured like the antenna 1000 illustrated in FIG. 10. Such atransmitter may communicate with a receiver, also configured like theantenna 1000 illustrated in FIG. 10.

As illustrated in FIG. 10, in either of the above described cases (i.e.,whether the antenna 1000 is acting as a transmitter or a receiver), thepolarization radiated by or accepted by the polarization-modificationchannels 702 is at an angle with respect to the waveguide antennaelements 902. This corresponding angle may be between 44 and 46 degrees(e.g., 45 degrees), for example. A variety of alternate angles may alsobe used in various embodiments. In still other embodiments, thepolarization-modification channels 702 need not all be disposed at thesame angle relative to waveguide antenna elements 902. This could allowa corresponding antenna to radiate and receive electromagnetic waveshaving a variety of polarizations, for example. In yet otherembodiments, the polarization-modification channels 702 need not be allthe same size and shape as one another. This could allow a correspondingantenna to radiate and receive electromagnetic waves having a variety ofpolarizations (e.g., if the polarization-modification channels 702 werecircular rather than stadium-shaped) and/or a variety of frequencies(e.g., if the polarization-modification channels 702 were sized suchthat they were resonant at different frequencies), for example. Evenfurther, one or more of the polarization-modification channels 702 couldbe filled with a material (e.g., a dielectric material), thereby furtherchanging one or more of the properties (e.g., resonant frequency) of theassociated electromagnetic waves which could propagate through thecorresponding polarization-modification channel 702.

In some embodiments, two or more polarization-modification layers 700could be cascaded on top of the waveguide antenna elements 902. If therewere multiple polarization-modification layers 700 cascaded on top ofthe waveguide antenna elements 902, the correspondingpolarization-modification channels 702 could provide increased frequencybandwidth over which electromagnetic waves could be radiated or receivedby the corresponding antenna. Further, cascading multiplepolarization-modification layers 700 could permit an angle ofpolarization radiated or received to be greater or less than the angleillustrated in FIG. 10. For example, an alternate antenna may have twocascaded polarization-modification layers. The first layer could be atan angle between 20 and 25 degrees with respect to the array ofwaveguide antenna elements 902, and the second layer could be at anbetween 20 and 25 degrees with respect to the first layer. In this way,the angle of polarization rotation undergone by electromagnetic waves(i.e., 45 degrees) would be the same as in the embodiment of FIG. 11,but the bandwidth could be increased.

The design of the antenna 1000 illustrated in FIG. 10 could also serveto reduce interference between two separate antennas. For example, aradar system could employ two antennas having analogous designs, but thepolarization-modification channels within the polarization-modificationlayer of one antenna are rotated at an angle that is orthogonal to thepolarization-modification channels within the polarization-modificationlayer of the other antenna. In an alternative example, two separateantennas could have polarization-modification layers withpolarization-modification channels oriented at a parallel angle with oneanother, but be facing one another (e.g., if the antennas were mountedin the same orientation on vehicles travelling in opposite directions).Either of the above methods could reduce interference because the twoantennas employ orthogonal polarizations. Therefore, cross polarizationisolation may occur between the two antennas. For example, a signaloutput by one antenna may be attenuated by as much as 40 dB (decibels)when transmitted through the polarization-modification layer of theother antenna.

FIG. 11 illustrates an array of waveguide antenna elements 902, apolarization-modification layer 700, and an array of waveguide outputports 1102, according to example embodiments. As illustrated, theembodiment illustrated in FIG. 11 may be analogous to the embodimentillustrated in FIG. 10 with an addition of an array of waveguide outputports 1102. The array of waveguide antenna elements 902, thepolarization-modification layer 700, and the array of waveguide outputports 1102, in addition to the phase adjusting section 910 and thewaveguide input 912 may form an antenna 1100. Further, the antenna 1100may be designed to radiate or receive electromagnetic waves in a TE₁₀waveguide mode.

The antenna 1100 could be used to transmit and/or receiveelectromagnetic waves (e.g., radio waves) for a variety of purposes(e.g., navigation within an autonomous vehicle using radar or radiocommunication). In further embodiments, the antenna 1100 may have agreater or lesser number of waveguide antenna elements 902, waveguideoutput ports 1102, and/or polarization-modification channels 702.Additionally or alternatively, the antenna 1100 may not have the phaseadjusting section 910 or the waveguide input 912. For example, one ormore of the individual waveguide antenna elements 902 may be fed byphotonic or electronic source(s) rather than feed waveguides connectedto the phase adjusting section 910 and the waveguide input 912.

In the embodiment of FIG. 11, the waveguide antenna elements 902 couldoutput electromagnetic waves, for example. These electromagnetic wavesmay then propagate to the polarization-modification channels 702. Thepolarization-modification channels 702 may then serve to rotate thepolarization of the associated electromagnetic waves by a defined angle(e.g., 45 degrees). The electromagnetic waves, now having anintermediate polarization, may then be transmitted to the waveguideoutput ports 1102. The waveguide output ports 1102 may be designed ofsufficient length so as to assure that any evanescent waves, which aretransmitted from the polarization-modification channels 702 to thewaveguide output ports 1102, are sufficiently attenuated before reachingradiation ports located at an end of the waveguide output ports 1102.Upon entering the waveguide output ports 1102, the electromagnetic wavesmay undergo another polarization rotation (e.g., by an additional 45degrees). The associated electromagnetic waves, now having apolarization rotated by a given angle relative to the waveguide antennaelements 902 (e.g., a polarization rotated by 45 or 90 degrees; theinput polarization thus being orthogonal to the output polarization) maythen be radiated to the environment upon exiting the waveguide outputports 1102. This process could also occur in the pseudo-inverse toreceive electromagnetic waves using the same antenna 1100 (i.e.,electromagnetic waves are received by the waveguide output ports 1102,the polarization is rotated upon entering the polarization-modificationchannels 702, the polarization is rotated again upon entering thewaveguide antenna elements 902, and then the electromagnetic waves aretransmitted to one or more devices attached to the antenna having beenrotated in polarization twice).

In some embodiments, as illustrated in FIG. 11, the number of waveguideantenna elements 902 within the array, the number ofpolarization-modification channels 702 defined within thepolarization-modification layer 700, and the number of waveguide outputports 1102 within the array will all be the same. In some embodiments,there may be greater or fewer waveguide output ports 1102 thanpolarization-modification channels 702, which may in turn be greater orfewer than the number of waveguide antenna elements 902. Further, thearrangement of the array of waveguide output ports 1102 may notcorrespond to the arrangement of the polarization-modification channels702, as illustrated in FIG. 11. In some embodiments, for example, thearray of waveguide output ports 1102 may be spaced irregularly ordifferently from the spacing of the polarization-modification channels702.

As illustrated in FIG. 11, each of the waveguide output ports 1102 isrotated the same amount with respect to the underlyingpolarization-modification channel 702 (e.g., between 44 and 46 degrees).Further, each of the polarization-modification channels 702 is rotatedthe same amount with respect to the underlying waveguide antenna element902 (e.g., between 44 and 46 degrees). As such, in the antenna 1100 ofFIG. 11, each of the waveguide output ports 1102 is rotated an equalamount with respect to the underlying waveguide antenna elements 902(e.g., between 88 and 92 degrees). Other angles besides thoseillustrated in FIG. 11 are also possible. For example, the angle betweenthe polarization-modification channels 702 and the waveguide antennaelements 902 could be 15 degrees, and the angle between thepolarization-modification channels 702 and the waveguide output ports1102 could be 15 degrees, resulting in an angle between the waveguideoutput ports 1102 and the waveguide antenna elements 902 of 30 degrees.

In some embodiments, the rotation of the waveguide output ports 1102relative to the polarization-modification channels 702 and/or thewaveguide antenna elements 902 may vary among the waveguide output ports(e.g., one waveguide output port is rotated 75 degrees with respect tothe underlying waveguide antenna element and another is rotated 90degrees with respect to the underlying waveguide antenna element). Sucha variation could leave to multiple polarization angles being emitted bythe antenna 1100, for example. Further, such a variation in angles couldcause the corresponding arrangement of waveguide output ports within thearray or the corresponding size/shape of various waveguide output portsto change to accommodate such differences.

Additionally, as described above, one or more of the waveguide guideoutput ports 1102 could additionally or alternatively be rotated aboutan axis parallel to the planar surface of the polarization-modificationlayer 700 (as opposed to rotated about the vertical axis that is normalto the planar surface of the polarization-modification layer 700). Thiscould allow for directionality of the antenna 1100, for example.

As illustrated in FIG. 11, the waveguide output ports 1102 are shaped asrounded rectangles. Further, dimensions associated with the output ports1102 illustrated in FIG. 11 may correspond to specific wavelengths ofelectromagnetic waves that are to be transmitted and/or received by theantenna 1100 (e.g., wavelengths associated with electromagnetic waveshaving a frequency of 77 GHz). However, one or more of the waveguideoutput ports 1102 could be replaced by alternately shaped and/or sizedoutput ports (e.g., a horn antenna or a substantially circularwaveguide). Still further, the waveguide output ports 1102 mayadditionally or alternatively be wholly or partially filled with amaterial other than air (e.g., a dielectric material). Any of thesefactors (e.g., shape, size, or filling of the waveguide output ports1102), as well as other factors, could enhance or reduce filteringcharacteristics associated with the antenna 1100. For example, if one ormore of the waveguide output ports 1102 were filled with a dielectric,the resonant wavelength associated with the respective waveguide outputport(s) 1102 may be altered, thus enhancing or diminishing thetransmission of specific wavelengths through the respective waveguideoutput port(s) 1102.

Described above analogously, multiple layers of waveguide output port1102 arrays could be cascaded. This could increase the bandwidth offrequencies which could effectively be used with the antenna 1102, forexample. Further, such a cascading could increase or decrease an anglebetween the waveguide output ports 1102 and the waveguide antennaelements 902. Additionally or alternatively, alternating layers ofpolarization-modification layers 700 followed by waveguide output port1102 array layers could be cascaded to achieve similar effects. Forexample, an alternate antenna design may include an array of waveguideantenna elements, followed by two polarization-modification layers,followed by an array of waveguide output ports. In such a design, therecould be an angle between each successive layer performing additionalpolarization rotation (e.g., the polarization-modification channels inthe first polarization-modification layer are at an angle, e.g. 25 to 35degrees, with respect to the array of waveguide antenna elements, thepolarization-modification channels within the secondpolarization-modification layer are at another angle, e.g. 25 to 35degrees, with respect to the polarization-modification channels in thefirst polarization-modification layer, and the array of waveguide outputports are at yet another angle, e.g. 25 to 35 degrees, with respect tothe polarization-modification channels in the secondpolarization-modification layer). In addition, the angles, sizes,shapes, distributions, or numbers of waveguide output ports 1102 and/orpolarization-modification channels 702 within such cascaded layers mayvary from layer to layer.

FIGS. 12-13 show further configurations of antennas having apolarization rotation integrated in the throat of the DOEW that canprovide desired power division ratios, an impedance match for all (or asubset) of ports using one or multiple steps, ridges, or a combination.The example antennas shown can provide the desired twisted polarizationof electromagnetic waves while also having the ability to maintain acompact size and location overall. In some instances, the antennas shownin FIG. 12-13 may include a rotation portion that is integrated into atop portion of the antenna block. Thus, unlike the previous description,the polarization twist may be achieved within the split-block antennastructure, therefore a polarization filter may not be used to achievethe polarization rotation.

FIG. 12A illustrates example twisted antenna configuration 1200. Asshown, antenna configuration 1200 includes radiating elements 1202,1204, 1206, and 1208 that each may transmit or receive radar signals aspart of a radar unit. The configuration of radiating elements 1202-1208can adjust the polarization at which each radiating element 1202-1208transmits or receives radar signals. For example, the innerconfiguration 1200 may be configured to twist the polarization of radarsignals transmitted or received by ninety (90) degrees.

In some examples, the twisted configuration of radiating elements1202-1208 relative to the waveguide of antenna configuration 1200 mayadjust the polarization of electromagnetic waves transmitted or receivedby forty-five degrees. For instance, radiating elements 1202-1208 maycause radar signals to be transmitted at a slanted, forty-five degreesfrom horizontal polarization instead of a vertical linear polarization.In other examples, radiating elements 1202-1208 can adjust polarizationof radar signals to a greater or lesser extent. As an example, theconfiguration of radiating elements 1202-1208 may adjust thepolarization by ninety-degrees (e.g., from horizontal linearpolarization to vertical linear polarization). In further examples, theextent of polarization modification can differ among the set ofradiating elements 1202-1208.

FIG. 12B illustrates another twisted antenna configuration 1210. Asshown, antenna configuration 1210 includes twisted radiating elements1212, 1214, 1216, 1218, 1220, and 1222. In other examples, theconfiguration, quantity or radiating elements, and other parameters ofantenna configuration 1210 can differ.

Radiating elements 1212-1222 connect to an inner serial feedingwaveguide of antenna configuration 1210 in a manner that adjusts theperformance of antenna configuration 1210. In, particular, the twistedconfiguration can modify operation of radiating elements 1212-1222 suchthat each radiating element operates in a different polarization asdesired. For example, radiating elements 1212-1222 may transmit orreceive radar signals in a slanted polarization (e.g., a slantedpolarization at positive or negative forty-five degrees fromhorizontal). In other examples, the extent of modification ofpolarization of radar signals can vary depending on the configuration ofradiating elements 1212-1222. For instance, radiating elements 1212-1222may alter the polarization of electromagnetic waves by ninety degrees(90 degrees) depending on the configuration of radiating elements1212-1222 relative to the waveguide of antenna configuration 1210.Further, the type of feed (e.g., parallel, serial) directingelectromagnetic waves into the waveguide can differ within examples.

FIG. 13 illustrates a twisted antenna 1300. As shown in FIG. 13,waveguide 1304 may include multiple radiating elements (shown as1302A-1302E). Although radiating elements 1302A-1302E are shown asdoublets, other radiating structures may be use as well. For example,singlets, and any other radiating structure that can be coupled to awaveguide may be in other example implementations.

Waveguide 1304 may include various shapes and structures configured todirect electromagnetic power to the various radiating elements1302A-1302E coupled to waveguide 1304. A portion of electromagneticwaves propagating through waveguide 1304 may be divided and directed byvarious recessed wave-directing member and raised wave-directingmembers. The pattern of wave-directing members shown in FIG. 13 is oneexample for the wave-directing members. Based on the specificimplementation, the wave-directing members may have different sizes,shapes, and locations.

At each junction of one of the respective radiating elements 1302A-1302Eof waveguide 1304, the junction may be considered a two-way powerdivider. As such, a percentage of the electromagnetic power may coupleinto the neck of the respective radiating elements 1302A-1302E and theremaining electromagnetic power may continue to propagate down waveguide1304. By adjusting various parameters (e.g., neck width, heights, andsteps) of each respective radiating element 1302A-1302E, the respectivepercentage of the electromagnetic power may be controlled while animpedance match is maintained in all affected ports associated with thepower divider. Thus, the geometry of each respective radiating element1302A-1302E may be controlled in order to achieve the desired powertaper. The adjustments of the geometry of each of the offset feed andeach respective radiating element 1302A-1302E can cause the desiredpower taper for waveguide 1304 and associated radiating elements1302A-1302E may be achieved.

Electromagnetic energy may be injected into the waveguide 1304 via awaveguide feed. For instance, the waveguide feed may be a port (e.g., athrough-hole) in a bottom metal layer, in some embodiments. Anelectromagnetic signal may be coupled from outside the antenna unit intowaveguide 1304 through the waveguide feed. The electromagnetic signalmay come from a component located outside the antenna unit, such as aprinted circuit board, another waveguide, or other signal source. Insome examples, the waveguide feed may be coupled to another dividingnetwork of waveguides.

In some examples, the present system may operate in one of two modes. Inthe first mode, the system may receive electromagnetic energy from asource for transmission (i.e., the system may operate as a transmissionantenna). In the second mode, the system may receive electromagneticenergy from outside of the system for processing (i.e., the system mayoperate as a reception antenna). In the first mode, the system mayreceive electromagnetic energy at a waveguide feed, divide theelectromagnetic energy for transmission by a plurality of radiatingelements, and radiate the divided electromagnetic energy by theradiating elements. In the second mode, the system may receiveelectromagnetic energy at the plurality of radiating elements, combinethe received electromagnetic energy, and couple the combinedelectromagnetic energy out of system for further processing.

As further shown in FIG. 13, radiating elements 1302A-1302E are eachshown in a rotated position. Particularly, the rotation can adjusts theperformance of each radiating element causing radiating elements1302A-1302E to operate in a different polarization as desired. Forexample, the twisted configuration of radiating elements 1302A-1302E cancause radiating elements 1302A-1302E to receive the divided andpre-twisted electromagnetic waves from the neck and subsequently adjustthe polarization of the electromagnetic waves to a desired polarization(e.g., slanted forty-five degrees from horizontal). The configurationbetween waveguide 1304 and radiating elements 1302A-1302E includessufficient propagation paths that can stabilize the electromagneticwaves. The stabilization of the electromagnetic waves can also diminishor even eliminate parasitic evanescent waves associated with twistedantenna 1300. As a result of the configuration and propagation paths oftwisted antenna 1300, only desired propagating electromagnetic waves maysurvive in the desired twisted angle.

Additionally, waveguide 1304 may be designed to have waveguide ends1306A and 1306B to be tuned shorts. For example, the geometry of theends of the waveguides may be adjusted so waveguide ends 1306A and 1306Bact as tuned shorts. In some implementations, waveguide ends 1306A,1306B or other components can provide an impedance match to free spaceat the end of waveguide 1304. As such, twisted antenna 1300 may radiatethe electromagnetic waves into free space with no reflection.

It should be understood that other shapes, configurations, anddimensions of the waveguide channels, portions of the waveguidechannels, sides of the waveguide channels, wave-directing members, andthe like are possible as well. In some embodiments, a rectangular shapeof waveguide channels may be highly convenient to manufacture, thoughother methods known or not yet known may be implemented to manufacturewaveguide channels with equal or even greater convenience. In furtherexamples, radiating elements 1302A-1302E may have a differentconfiguration relative to waveguide 1304 such that radiating elements1302A-1302E transmit or receive radar signals at different polarizationsas desired.

In addition, some examples can include a subset of radiating elements1302A-1302E to have different configurations such that the subsetoperates in a different polarization compared to other radiatingelements of twisted antenna 1300. For instance, radiating elements1302A, 1302B, and 1302C may be configured to operate in a firstpolarization and radiating elements 1302D, 1302E may be configured tooperate in a second polarization that differs from the firstpolarization. Antenna 1300 may be part of a radar system that operatesin one or multiple polarizations to reduce potential jamming with radarfrom other systems. Further, the configuration of antenna 1300 canenhance the signal-to-noise ratio (SNR) reducing unwanted noise whileantenna 1300 operates.

FIG. 14 illustrates a method 1400 of radiating electromagnetic waves,according to example embodiments. The method 1400 may be performed usingthe antenna 1100 illustrated in FIG. 11, in some example embodiments.Further, the method 1400 could be performed pseudo-inversely to receiveelectromagnetic waves (as opposed to radiate), in some embodiments. Themethod 1400 may be performed to aid in navigation of an autonomousvehicle using a radar system mounted on the autonomous vehicle, forexample. Alternatively, the method 1400 may be performed to communicateusing radio communication techniques.

At block 1402, the method 1400 includes emitting electromagnetic waveshaving a first polarization from a plurality of waveguide antennaelements in a first array. The waveguide antenna elements in the firstarray may resemble the array of waveguide antenna elements 902illustrated in FIG. 9, for example. As an example, a radar unit coupledto a portion (or built into a portion) of a vehicle may emitelectromagnetic waves.

At block 1404, the method 1400 includes receiving, by channels definedwithin a polarization-modification layer that is disposed between thewaveguide antenna elements and a plurality of waveguide output portsarranged in a second array, the electromagnetic waves having the firstpolarization. The channels may be oriented at a first angle with respectto the waveguide antenna elements. The first angle may be between 44 and46 degrees (e.g., 45 degrees), for example. Further, thepolarization-modification layer and the channels may be thepolarization-modification layer 700 and the polarization rotatingchannels 702, respectively, illustrated in FIG. 7, for example. Stillfurther, the waveguide output ports may be the waveguide output ports1102 illustrated in FIG. 11, for example.

At block 1406, the method 1400 includes transmitting, by the channelsdefined within the polarization-modification layer, electromagneticwaves having an intermediate polarization.

At block 1408, the method 1400 includes receiving, by the waveguideoutput ports, electromagnetic waves having the intermediatepolarization. The waveguide output ports may be oriented at a secondangle with respect to the channels. The second angle may be between 44and 46 degrees (e.g., 45 degrees), for example.

At block 1410, the method 1400 includes radiating, by the waveguideoutput ports, electromagnetic waves having a second polarization. Thesecond polarization may be different from the first polarization. Thesecond polarization may also be different from the intermediatepolarization. Further, the first polarization may be different from theintermediate polarization. The first polarization, intermediatepolarization, and second polarization could be the following,respectively: a horizontal TE₁₀ polarization, a TE₁₀ polarization at a45-degree angle between horizontal and vertical, and a vertical TE₁₀polarization.

It should be understood that other shapes and dimensions of thewaveguide channels, portions of the waveguide channels, sides of thewaveguide channels, wave-directing members, and the like are possible aswell. In some embodiments, a rectangular shape, or a rounded rectangularshape, of waveguide channels may be highly convenient to manufacture,though other methods known or not yet known may be implemented tomanufacture waveguide channels with equal or even greater convenience.

In some examples, an antenna configuration may include a plurality ofwaveguide antenna elements arranged in a first array configured tooperate with a first polarization and a plurality of waveguide outputports arranged in a second array configured to operate with a secondpolarization. Particularly, the second polarization may differ from thefirst polarization (e.g., orthogonal to each other). The antennaconfiguration may also include a polarization-modification layer withchannels defined therein such that the polarization-modification layeris disposed between the waveguide antenna elements and the waveguideoutput ports. As such, the channels may be oriented at a first anglewith respect to the waveguide antenna elements and at a second anglewith respect to the waveguide output ports. For instance, the firstangle may be between 44 and 46 degrees and the second angle may bebetween 44 and 46 degrees. In addition, the channels may be configuredto receive input electromagnetic waves having the first polarization andtransmit output electromagnetic waves having a first intermediatepolarization. Similarly, the waveguide output ports may be configured toreceive input electromagnetic waves and radiate electromagnetic waveshaving the second polarization.

In further examples, the waveguide antenna elements and the waveguideoutput ports may be substantially rectangular in shape. In otherexamples, the waveguide antenna elements and the waveguide output portsmay be substantially circular in shape. Further, the channels may beshaped as round rectangles and the channels may be filled with adielectric material. In some instances, the thickness of thepolarization-modification layer may vary. For example, the thickness ofthe polarization-modification layer may be between a half and a wholewavelength of the input electromagnetic waves having the firstpolarization.

In addition, some examples may also involve a secondarypolarization-modification layer with secondary channels defined therein.Particularly, the secondary polarization-modification layer may bedisposed between the polarization-modification layer and the waveguideoutput ports and the secondary channels may be oriented at a third anglewith respect to the waveguide antenna elements and at a fourth anglewith respect to the waveguide output ports. Further, the secondarychannels may be configured to receive input electromagnetic waves havingthe first intermediate polarization and transmit output electromagneticwaves having a second intermediate polarization. As such, the firstintermediate polarization may differ from the second intermediatepolarization. As an example, a bandwidth of usable frequenciesassociated with the radar antenna may lie within the 77 GHz band. Insome instances, the first angle may be between 25 and 35 degrees, thesecond angle may be between 50 and 70 degrees, the third angle may bebetween 50 and 70 degrees, and the fourth angle may be between 25 and 35degrees. Other degrees for the angles are possible.

Further, it should be understood that other layouts, arrangements,amounts, or sizes of the various elements illustrated in the figures arepossible, as well. For example, it should be understood that a givenapplication of an antenna or antenna system may determine appropriatedimensions and sizes for various machined portions of thepolarization-modification unit cells illustrated in the figures (e.g.,channel size, metal layer thickness, etc.) and/or for other machined (ornon-machined) portions/components of the antenna(s) and antennasystem(s) described herein. For instance, as discussed above, someexample radar systems may be configured to operate at an electromagneticwave frequency of 77 GHz, which corresponds to millimeterelectromagnetic wave length. At this frequency, the channels, ports,etc. of an apparatus may be of given dimensions appropriated for the 77GHz frequency. Other example antennas and antenna applications arepossible as well.

Still further, the word “antenna” should not be limited to applicationsinvolving electromagnetic waves solely within radio frequencies of theelectromagnetic spectrum. The term “antenna” is used herein broadly todescribe a device that is capable of transmitting and/or receiving anyelectromagnetic wave. For example, any of the antennas or components ofthe antennas described herein could be capable of transmitting and/orreceiving optical light. Even further, any of the antennas or componentsof the antennas described herein could be capable of being fed byoptical sources (e.g., optical fibers or optical lasers). Such exampleantennas could be used as optical interconnects within a computingdevices, for instance. In addition, corresponding shapes and dimensionsof components within such antennas may vary depending on the wavelength(e.g., components used in optical embodiments may have feature sizes onthe scale of hundreds of nanometers as opposed to millimeter featuresizes in radio embodiments). In addition, radar units may operate as apart of a vehicle radar system. As such, a radar unit may be positionedon a vehicle component, built into a vehicle component, or a combinationin some examples.

It should be understood that arrangements described herein are forpurposes of example only. As such, those skilled in the art willappreciate that other arrangements and other elements (e.g., machines,apparatuses, interfaces, functions, orders, and groupings of functions,etc.) can be used instead, and some elements may be omitted altogetheraccording to the desired results. Further, many of the elements that aredescribed are functional entities that may be implemented as discrete ordistributed components or in conjunction with other components, in anysuitable combination and location.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the scope beingindicated by the following claims.

What is claimed is:
 1. An antenna, comprising: a waveguide antennaelement; a waveguide output port; a polarization-modification layer witha channel defined therein; and a rotation component coupled to thepolarization-modification layer, wherein the polarization-modificationlayer is disposed between the waveguide antenna element and thewaveguide output port, and wherein the rotation component is configuredto adjust an orientation of the polarization-modification layer relativeto the waveguide antenna element and the waveguide output port such thatsubsequent electromagnetic waves radiated by the waveguide antennaelement have a different polarization.
 2. The antenna of claim 1,wherein the waveguide antenna element and the waveguide output port aresubstantially rectangular in shape.
 3. The antenna of claim 1, whereinthe waveguide antenna element and the waveguide output port aresubstantially circular in shape.
 4. The antenna of claim 1, wherein thechannel is shaped as a rounded rectangle.
 5. The antenna of claim 1,wherein a thickness of the polarization-modification layer is between ahalf and a whole wavelength of input electromagnetic waves.
 6. Theantenna of claim 1, wherein the channel is filled with a dielectricmaterial.
 7. The antenna of claim 1, wherein a bandwidth of usablefrequencies associated with radiating electromagnetic waves using thewaveguide antenna element lies within a 77 GHz band.
 8. The antenna ofclaim 1, wherein the rotation component is a microelectromechanicalsystem (MEMs) device.
 9. The antenna of claim 1, further comprising: asecond waveguide element configured to receive electromagnetic wavereflections.
 10. A radar system comprising: a transmitter comprising: afirst waveguide antenna element; a first polarization-modification layerwith a first channel defined therein, wherein the firstpolarization-modification layer is disposed adjacent to the firstwaveguide antenna element; and a first rotation component coupled to thefirst polarization-modification layer, wherein the first rotationcomponent is configured to adjust an orientation of the firstpolarization-modification layer relative to the first waveguide antennaelement such that subsequent electromagnetic waves radiated by the firstwaveguide antenna element have a different polarization; and a receivercomprising: a second waveguide antenna element.
 11. The radar system ofclaim 10, wherein the receiver further comprises: a secondpolarization-modification layer with a second channel defined therein,wherein the second polarization-modification layer is disposed adjacentto the second waveguide antenna element; and a second rotation componentcoupled to the second polarization-modification layer, wherein thesecond rotation component is configured to adjust an orientation of thesecond polarization-modification layer relative to the second waveguideantenna element to enable the second waveguide antenna element toreceive subsequent electromagnetic waves having the differentpolarization.
 12. The radar system of claim 11, wherein the firstchannel and the second channel are shaped as rounded rectangles.
 13. Theradar system of claim 11, wherein the first rotation component and thesecond rotation component correspond to a microelectromechanical system(MEMs) device.
 14. The radar system of claim 13, wherein the radarsystem is coupled to a vehicle.
 15. The radar system of claim 11,wherein a thickness of the first polarization-modification layer is lessthan a wavelength of input electromagnetic waves having a givenpolarization.
 16. The radar system of claim 15, wherein the firstchannel and the second channel are filled with a dielectric material.17. A method, comprising: emitting electromagnetic waves having a firstpolarization from a waveguide antenna element on a radar unit, whereinthe waveguide antenna element is coupled to a waveguide output port witha polarization-modification layer disposed between the waveguide antennaelement and the waveguide output port; adjusting, using a rotationcomponent coupled to the polarization-modification layer, an orientationof the polarization-modification layer relative to the waveguide antennaelement and the waveguide output port; and based on adjusting theorientation of the polarization-modification layer, emittingelectromagnetic waves having a second polarization from the waveguideantenna element.
 18. The method of claim 17, further comprising:receiving reflections corresponding to the electromagnetic waves havingthe first polarization using a second waveguide antenna element on theradar unit.
 19. The method of claim 18, wherein adjusting theorientation of the polarization-modification layer relative to thewaveguide antenna element and the waveguide output port comprises:adjusting the orientation of the polarization-modification layerrelative to second waveguide antenna element such that second waveguideantenna element is configured to receive reflections corresponding tothe electromagnetic waves having the second polarization.
 20. The methodof claim 19, further comprising: based on measurements from the radarunit, providing a signal to the rotation component to adjust theorientation of the polarization-modification layer; and whereinadjusting the orientation of the polarization-modification layerrelative to the waveguide antenna element and the waveguide output portis responsive to providing the signal to the rotation component.